Evaporative Emission (EVAP) Purge Solenoid

EVAP Purge Solenoid:

The EVAP purge solenoid is located towards the rear of the air box. When the EVAP purge solenoid is commanded On, fuel vapors are drawn in to the engine via manifold vacuum supplied to the solenoid. As the solenoid is commanded On, fresh air flows around the normally open EVAP vent solenoid, through the EVAP canister. Vapors that are stored in the charcoal are drawn up through the EVAP purge solenoid to be consumed in the normal combustion process. The normally closed EVAP purge solenoid is commanded a certain duty cycle by the ECM in order to precisely control the vapor flow. The EVAP purge solenoid will also open and close during the EVAP Diagnostic System Test performed by the ECM necessary to perform EVAP leak diagnostics. NOTE: During normal purge mode, the ECM will not update the long term fuel trim cells. When purge mode is enabled, the ECM will use the previous stored long term fuel trim cell values. The ECM will periodically cycle the purge mode On and Off to update the long term fuel trim cells.